Acoustic measurement systems are used in a wide variety of applications, including industrial applications; such as in manufacturing, motion detection for security systems, and increasingly in automotive applications, among others. In automotive applications acoustic measurement can be used for detecting the distance, as well as the rate of change of distance, between the vehicle and objects in the vicinity of the vehicle. This is particularly useful in collision warning/avoidance applications and parking assist applications. Acoustic pulses are transmitted from the vehicle and any obstacles within sufficient range reflect the acoustic pulses. The echo time and Doppler frequency shift of the reflected pulse can be used to derive information about the distance to the object as well as whether the object is moving towards or away from the vehicle, and at what rate.
As the use of acoustic distance measurement systems increases in vehicular applications, there is an increasing chance that vehicles using such systems will interfere with each other's systems. Vehicles using the same or similar frequencies in proximity to each other will experience “cross talk,” which occurs when one vehicle receives acoustic signals from another vehicle and is unable to distinguish the signal from its own signal. Such cross talk can result in false detections, resulting in incorrect distance and Doppler shift measurements, compromising the effectiveness of collision alert/avoidance systems. Furthermore, there can be a significant amount of acoustic noise in automotive and other applications which affects the effectiveness of acoustic receivers. Accordingly, there is a need for a means by which the effect of cross talk can be suppressed.